• Create a new course in topics format
• Add a new topic
• Click "Add a new activity" in the topic that was just added
• Two activity choosers open (you can see it if you close one without selecting an activity)

I just spent two hours trying to figure out why behat is failing in my addon course format when I run it on 4.2 and it turned out that this scenario was covered in my behat test but was not covered in the core.